Method of bleaching sole leather



OB S O J. RAISOR METHOD OF BLEACHING SOLE LEATHER musbg Filed Jan. 2 1922 SR. hum-8,686

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iC/lllON Qt TEXTTLES (ii HBERS, I i D? Patented June 15, 1926 JACOB RAISOR, 0F HORNELL, NEW YORK, ASSIGNOR OF ONE-THIRD TO DUDLEY S. MEBSEREAU AND ONE-THIRD TO JOHN M. PAYNE, BOTH OF ENDICO'IT, NEW YORK.

METHOD OF BLEAGHING SOLE LEATHER.

Application filed. January 25, 1922.. Serial No. 581,725.

This invention relates to a method of bleaching sole leather or the like.

As is of common knowledge in the pres ent art, the sides of leather when taken from a tannery are red in color and must be bleached before being rolled and dried. Heretofore the practise has been to dip the sides of leather into an alkali solution and then to dip the leather in a sulphuric acid solution to remove the alkali. After this the leather is dipped into water and then dried.

Upon drying the sole leather it has been observed that spots occur in the same, showing the alkali has notbeen entirely removed. Also the leather when dried sometimes cracks and usually is of less weight than previous to the time of subjecting the same to the bleaching process.

With that heretofore related in view, it is the object of the present invention to provide an improved method of bleaching sole leather or the like; which consists in dipping the leather in a number of different solutions adapted to produce a product, after be ing dried, which is uniform in color, not subject to cracking, and substantially of the same weight as at the time previous to submitting the leather to bleaching process.

The invention is illustrated by way of example in the accompanying drawing.

The present invention consists in providing aplurality of vats, preferably five in number, and numbering these tanks in the order of 1. 2, 3, i and 5 as shown. The vat No. 1 is filled with water. The vat No. 2 is filled with a solution of tanners alkali which is a common expedient for removing the coloring from leather at the time when received from the tannery The vat No. 3 is filled with a solution of water, sulphuric acid, alum and salt. The proportions for this solution would be approximately as follows: sulphuric acid 200 lbs., alum 200 lbs, salt 200 lbs. and sufiicient water to bring the solution to about 40 (Baum).

The vat No. 4 is filled with a weak solution of sulphuric acid and water, about 20 (Baum). The vat No. 5 is filled with water, the same as vat No. 1. The liquid in each of the vats should be heated to about 120 F. by steam or other convenient heating medium and so maintained.

In practicing the present method one or more sides of leather are dipped separately into the liquid of each vat, preferably for a period of five minutes. The liquid in each vat should be maintained at approximately 120 F. When dipped in vat No. 1 containing water the leather is softened and it is important that the temperature of the water be approximately 120 F. This is the first step in the present process.

The second step is to dip the leather into vat No. 2. The alkali solution opens the pores of the leather, and the coloring matter retained from previous tanning is permitted to escape. The leather becomes black in color due to the effect of the alkali solution. The sides of leather should now be taken from vat N0. 2 and dipped into vat No. 3 which constitutes the most important step of the process. In this dipping the sulphuric acid well neutralizes the alkali and causes the bleaching of the leather. The alum sets the color of the leather and also toughens the leather. The alum therefore performs a two-fold function. The salt performs the important function of giving back to the leather the weight which it has lost when dipped into the alkali solution in vat No. 2. This greatly adds to the pliability of the leather and in an obvious manner increases its selling quality.

From vat No. 3 the sides of leather is transferred to vat No. i and into the weak solution of sulphuric acid for cleansing. This additional treatment with the weak solution of sulphuric acid is exceedingly important in that the leather is thoroughly cleansed of any alkali, and when dried and rolled will produce a finished product with a uniform color.

Lastly the leather is dipped into vat No. 5 which contains pure water. The purpose of this dipping is to thoroughly cleanse the leather. The sides of leather may be now taken to the drying lofts.

It has been found from experience that the sides of leather dipped for bleaching in accordance with my invention, produce a product which is not subject to cracking, which maintains a uniform color, and which retains substantially the same weight as previous to being submitted to the bleaching process.

I claim 1. The herein described process of bleaching leather which consists in dippmg the leather into water having a temperature of approximately 120 F., then dipping the leather into an alkali solution, then dipping the leather into a solution of Water and equal parts by Weight of sulphuric acid, salt and alum, the quantity of Water employed being suflicient to bring the solution to approximately 40 Baum, and lastly dipping the leather into a Weak solution of sulphuric acid and Water of approximately 20 aum.

2. The herein described process of bleaching leather which consists of dipping the leather into Water having a temperature of 120 F., and permittitng the leather to remain in the Water for approximately five minutes, dipping the leather into an alkali solution a corresponding interval of time, then dipping the leather into a soluton of Water and equal parts by Weight of sulphuric acid, salt and alum a shorter length 20 of time, and then dipping the leather into a Weak solution of sulphuric acid and Water, said last solution being approximately 20 Baum.

JACOB RAISOR. 

